The present invention relates to an arrangement for controlling the propulsion or forward drive regulation of motor vehicles in the sense of the reduction of an undesired slippage of the wheels to be regulated in motor vehicles equipped with multi-axle drive.
An arrangement of this type has been proposed in German Pat. No. 35 45 546, in which for four-wheel drive vehicles with a drive slippage regulation (DSR), the signal of a vehicle longitudinal acceleration transmitter is used as a basis of the vehicle velocity reference control signal, which, however, makes relatively high demands as regards its evaluation.
It is the object of the present invention to so construct an arrangement of the aforementioned type wherein a reference signal can be formed without direct evaluation of a signal of a vehicle longitudinal acceleration transmitter.
The underlying problems are solved according to the present invention in that all of the velocity signals are obtained from the rotational speed signals from each of the four driven wheels and are fed to a device for the formation of a vehicle velocity reference signal, to a comparator circuit and also to a differentiating element. The reference signal is formed initially with a predetermined slope derived from a velocity signal corresponding to the minimum wheel velocity. The comparator circuit produces an output signal when a velocity signal exceeds the reference signal by a predetermined difference which initiates by way of an AND element, a first regulating cycle for reducing the driving torque of the vehicle engine at the adjusting element with a blocking signal at the output of a differentiating element when a negative acceleration value derived from the velocity signal exceeds a predetermined negative acceleration value which is fed to one inverting input of the AND element for controlling the adjusting element. The driving torque is kept constant during the regulating cycle phase of the negative acceleration, in that upon disappearance of the blocking signal--when dropping below the predetermined negative acceleration value--the adjusting element again increases the driving torque in the direction toward the value specified by the drive pedal. During the regulating cycle phase of negative acceleration, when the velocity signal drops below the reference-signal, the reference signal is now corrected in the reference signal-forming device to a velocity signal corresponding to a mimimum wheel velocity with a new slope for the following regulating cycle. Accordingly, a control of the driving torque is so selected that the wheel is guided during the regulation cycle in such a manner after termination of the regulation cycle, the stable range is reached. The reference velocity is thus set during each regulating cycle into the range of the optimum friction by the derivation of the reference velocity from the minimum wheel velocity.